Psychological scientists are very interested in this particular brand of irrational thinking — especially the link between conspiratorial thinking and anti-science world views. These plots and conspiracies may seem laughable at first glance, but they are not inconsequential. At the very least, conspiracy theorists waste a lot of time and at worst, they pose real dangers to society. Just think of how many parents, alarmed by the bogus link between vaccines and autism, have left their children unprotected against serious disease.

More than 90 percent of climate scientists agree that the global climate is shifting, largely as a result of human activity. Scientifically, this is essentially a closed case. Yet conspiracy theorists continue to spin wild tales of government agents surreptitiously destroying thermometers and burying contradictory evidence. What are the motives of these climate deniers...